/* ==========================================================================
    Modern CSS Custom Properties (Design Tokens)
    ========================================================================== */
:root {
    /* Modern Typography Stack */
    --font-primary: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    --font-display: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    --font-mono: 'JetBrains Mono', ui-monospace, 'Cascadia Code', 'Source Code Pro', Menlo, Consolas, monospace;
    
    /* Typography Scale */
    --font-size-xs: 0.75rem;
    --font-size-sm: 0.875rem;
    --font-size-base: 1rem;
    --font-size-lg: 1.125rem;
    --font-size-xl: 1.25rem;
    --font-size-2xl: 1.5rem;
    --font-size-3xl: 1.875rem;
    --font-size-4xl: 2.25rem;
    --font-size-5xl: 3rem;
    --font-size-6xl: 3.75rem;
    
    /* Line Heights */
    --line-height-tight: 1.25;
    --line-height-snug: 1.375;
    --line-height-base: 1.5;
    --line-height-relaxed: 1.625;
    --line-height-loose: 1.75;
    
    /* Modern Color System */
    --color-slate-50: #f8fafc;
    --color-slate-100: #f1f5f9;
    --color-slate-200: #e2e8f0;
    --color-slate-300: #cbd5e1;
    --color-slate-400: #94a3b8;
    --color-slate-500: #64748b;
    --color-slate-600: #475569;
    --color-slate-700: #334155;
    --color-slate-800: #1e293b;
    --color-slate-900: #0f172a;
    
    /* Air-inspired Primary Palette - Fresh Sky & Clouds */
    --color-primary: #87ceeb;
    --color-primary-50: #f0f8ff;
    --color-primary-100: #e1f1ff;
    --color-primary-200: #b8e0f5;
    --color-primary-500: #87ceeb;
    --color-primary-600: #6bb6dd;
    --color-primary-700: #4a9bc8;
    --color-primary-900: #2c5f7a;
    
    /* Air-inspired Secondary Palette - Blue Family */
    --color-secondary: #70d6ff;
    --color-secondary-50: #f0fbff;
    --color-secondary-100: #e0f7ff;
    --color-secondary-200: #a8e6ff;
    --color-secondary-300: #90e0ef;
    --color-secondary-400: #7dd3fc;
    --color-secondary-500: #70d6ff;
    --color-secondary-600: #4cbfdb;
    --color-secondary-700: #0ea5e9;
    --color-secondary-800: #0284c7;
    --color-secondary-900: #0c4a6e;
    --color-secondary-950: #082f49;
    
    /* Semantic Colors */
    --color-text: var(--color-slate-700);
    --color-text-light: var(--color-slate-600);
    --color-text-muted: var(--color-slate-500);
    --color-text-dark: var(--color-slate-900);
    --color-text-inverse: #ffffff;
    
    --color-background: #ffffff;
    --color-background-subtle: var(--color-primary-50);
    --color-surface: #ffffff;
    --color-surface-elevated: #fefefe;
    --color-surface-hover: var(--color-slate-50);
    
    --color-border: var(--color-slate-200);
    --color-border-light: var(--color-slate-100);
    --color-border-strong: var(--color-slate-300);
    
    /* Spacing System */
    --spacing-1: 0.25rem;
    --spacing-2: 0.5rem;
    --spacing-3: 0.75rem;
    --spacing-4: 1rem;
    --spacing-5: 1.25rem;
    --spacing-6: 1.5rem;
    --spacing-8: 2rem;
    --spacing-10: 2.5rem;
    --spacing-12: 3rem;
    --spacing-16: 4rem;
    --spacing-20: 5rem;
    --spacing-24: 6rem;
    --spacing-32: 8rem;
    
    /* Border Radius */
    --radius-none: 0;
    --radius-sm: 0.25rem;
    --radius-base: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    --radius-2xl: 1.5rem;
    --radius-3xl: 2rem;
    --radius-full: 9999px;
    
    /* Enhanced Shadow System */
    --shadow-xs: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-sm: 0 1px 3px 0 rgb(0 0 0 / 0.1), 0 1px 2px -1px rgb(0 0 0 / 0.1);
    --shadow-base: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --shadow-md: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 20px 25px -5px rgb(0 0 0 / 0.1), 0 8px 10px -6px rgb(0 0 0 / 0.1);
    --shadow-xl: 0 25px 50px -12px rgb(0 0 0 / 0.25);
    --shadow-2xl: 0 25px 50px -12px rgb(0 0 0 / 0.25);
    --shadow-inner: inset 0 2px 4px 0 rgb(0 0 0 / 0.06);
    
    /* Air-inspired Modern Gradients */
    --gradient-primary: linear-gradient(135deg, var(--color-primary-500) 0%, var(--color-primary-600) 100%);
    --gradient-secondary: linear-gradient(135deg, var(--color-secondary-500) 0%, var(--color-secondary-600) 100%);
    --gradient-surface: linear-gradient(135deg, #ffffff 0%, var(--color-primary-50) 100%);
    --gradient-hero: linear-gradient(135deg, var(--color-primary-100) 0%, var(--color-primary-50) 100%);
    
    /* Modern Transitions & Animations */
    --transition-all: all 200ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-base: 250ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-slow: 350ms cubic-bezier(0.4, 0, 0.2, 1);
    
    /* Animation Curves */
    --ease-in: cubic-bezier(0.4, 0, 1, 1);
    --ease-out: cubic-bezier(0, 0, 0.2, 1);
    --ease-in-out: cubic-bezier(0.4, 0, 0.2, 1);
    --ease-bounce: cubic-bezier(0.68, -0.55, 0.265, 1.55);
    
    /* Layout Constraints */
    --container-xs: 20rem;
    --container-sm: 24rem;
    --container-md: 28rem;
    --container-lg: 32rem;
    --container-xl: 36rem;
    --container-2xl: 42rem;
    --container-max: 80rem;
    --content-max-width: 65ch;
}